Power converter and control system for a motor using an inductive load and method of doing the same

• US 5,703,456 A
• Filed: 05/26/1995
• Issued: 12/30/1997
• Est. Priority Date: 05/26/1995
• Status: Expired due to Fees

• Current Assignee: Home Depot USA Incorporated (The Home Depot, Inc.)
• Original Assignee: Emerson Electric Company
• Inventors: Cox, Karmen D.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US08/452,419
• Time in Patent Office: 949 Days
• Field of Search: 318/138, 318/245, 318/254, 318/439, 318/699-813, 363/98, 363/95, 363/97, 363/53, 363/81, 363/89, 363/224, 363/207, 363/205
• US Class Current: 318/701
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02P 25/089 Sensorless control direct torque control H02P23/30
• CPC Class Codes: H02P 25/092 Converters specially adapted for controlling reluctance motors
• CPC Class Codes: H02P 25/0925 wherein the converter comprises only one switch per phase

Abstract

A power converter and controller system for a motor using an inductive load, such as a switched reluctance motor, which provides enhanced motor performance. The improved power converter and controller system accomplishes this by using a return bus having a storage device for storing energy. A controller monitors both the in the inductive load and the energy stored in the storage device and dynamically controls the storage device and the inductive load to dynamically control the current in the inductive load and the voltage on the storage device.

Claims

1. A power converter and control system for a motor having an inductive load, said system comprising:

a power converter having a supply bus electrically coupled to said inductive load, said supply bus supplying energy to said inductive load, said power converter having a return bus electrically coupled to said inductive load, said return bus electrically coupled to a storage device for storing energy; and

a controller provides control signals to said power converter, said control signals responsive to operating parameters of the inductive load and the return bus to dynamically activate/deactivate said inductive load.

2. The converter and control system according to claim 1 wherein said controller provides control signals responsive to the operating parameters of the inductive load and the return bus to dynamically control said return bus to dynamically control the energy stored in said storage device and the energy in said inductive load.

3. The power converter and control system according to claim 2 wherein said controller dynamically controls said energy stored in said storage device and said energy in said inductive load by dynamically 1) transferring energy from said storage device over said return bus to said inductive load when said current of to said inductive load is below a determined level and 2) transferring energy from said inductive load to said storage device when a) said energy stored in said storage device is below a second determined level and b) said energy of said inductive load is above a third determined level.

4. The power converter and control system according to claim 1 wherein said machine is a switch reluctance motor and said inductive load is a winding of said motor.

5. The power converter and control system according to claim 1 wherein said machine includes a plurality of windings, each of said windings having a first end, a second end, an energization switch and a current provided by said supply bus according to a control signal received by said energization switch for each of said windings.

6. The power converter and control system according to claim 1 wherein said return storage device is a capacitor.

7. The power converter and control system according to claim 6 wherein said capacitor is a relatively small size capacitor.

8. The power converter and control system according to claim 2 wherein said controller dynamically controls said energy stored in said storage device to a voltage level higher than said supply bus.

9. The power converter and control system according to claim 2 wherein said controller dynamically controls said energy stored in said storage device to a voltage level lower than a predetermined value.

10. The power converter and control system according to claim 2 wherein said controller dynamically controls said energy stored in said storage device by operating said power converter as a boost inverter.

11. A power converter and control system for a switched reluctance motor having N windings, each of said windings having a first end, a second end and an energization switch, said system comprising:

a power converter having a supply bus electrically coupled to said first end of each of said N windings and a common bus electrically coupled to said second end of each of said windings, said supply bus providing phase energies to said windings according to a first set of control signals received by energization switches for said windings, said power converter having a return bus electrically coupled to said windings and said common bus, said return bus having a return storage device for storing energy and a return bus switch; and

a controller provides control signals to said power converter, said control signals responsive to operating parameters of the windings and the return bus to dynamically activate/deactivate the energization switches for said windings.

12. The power converter and control system of claim 11 wherein said controller provides control signals responsive to the operating parameters of the windings and the return bus to dynamically control said return bus to dynamically control the energy stored in said storage device and the phase energy for a winding by dynamically switching between voltage levels across said winding.

13. The power converter and control system according to claim 11 wherein said controller dynamically controls said energy stored in said storage device and said phase energy for said winding by dynamically 1) transferring energy from said storage device over said return bus to said winding when said phase energy of said winding is below a determined level and 2) transferring energy from said winding to said storage device when a) said energy stored in said storage device is below a second determined level and b) said phase energy of said winding is above a third determined level.

14. The power converter and control system according to claim 11 wherein said storage device is a capacitor.

15. The power converter and control system according to claim 14 wherein said capacitor is a relatively small size capacitor.

16. The power converter and control system according to claim 11 wherein said controller dynamically controls said energy stored in said storage device to a voltage level higher than said supply bus.

17. The power converter and control system according to claim 11 wherein said controller dynamically controls said energy stored in said storage device to a voltage level lower than a predetermined value.

18. The power converter and control system according to claim 11 wherein said controller dynamically controls said energy stored in said storage device by operating said power converter as a boost inverter.

19. The power converter and control system according to claim 11 wherein said controller dynamically controls phase energy of a winding without pulse-width modulating said energization switch of said winding by dynamically controlling said energization switch depending on said phase energy and said voltage level of said storage device.

20. The power converter and control system according to claim 11 wherein said controller dynamically controls phase energy of a winding above a minimum energy level by invoking a braking function.

21. The power converter and control system according to claim 12 wherein said controller dynamically activates an energization switch for a winding having a low torque and inductance to store energy in said winding for said storage device.

22. A power converter and control methodology for a motor having an inductive load, said methodology comprising the steps of:

providing a power converter having a supply bus electrically coupled to a first end of said inductive load and a common bus electrically coupled to a second end of said inductive load, said supply bus supplying energy to said inductive load according to a control signal received by an energization switch, said power converter having a return bus, said return bus having a storage device for storing energy;

monitoring operating parameters for said inductive load and said return bus; and

dynamically activating/deactivating said inductive load in response to said operating parameters of said inductive load and said return bus.

23. The converter and control system methodology according to claim 22 further including the step of:

dynamically controlling said return bus in response to the operating parameters of said inductive load and said return bus to dynamically switch between voltage levels across said inductive load.

24. The power converter and control methodology according to claim 23 wherein said step of dynamically controlling said energy stored in said storage device and said energy in said inductive load further includes the step of:

dynamically transferring energy to said inductive load from said storage device when said energy of said inductive load is below a determined level; and

dynamically transferring energy to said storage device from said inductive load when a) said energy stored in said storage device is below a second determined level

and b) said energy of said inductive load is above a third determined level.

25. The power converter and control methodology according to claim 22 wherein said step of providing further includes the step of:

employing a switch reluctance motor as said motor and a winding of said motor as said inductive load.

26. The power converter and control methodology according to claim 25 wherein said step of employing further includes the step of:

employing a plurality of windings, each of said windings having a first end, a second end, an energization switch and energy provided by said supply bus according to said control signal received by said energization switch for each of said windings.

27. The power converter and control methodology according to claim 22 wherein said step of providing further includes the step of:

employing a capacitor as said storage device.

28. The power converter and control methodology according to claim 27 wherein said step of employing further includes the step of:

employing a relatively small size capacitor as said storage device.

29. The power converter and control methodology according to claim 23 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device to a voltage level higher than said supply bus.

30. The power converter and control methodology according to claim 23 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device to a voltage level lower than a predetermined value.

31. The power converter and control methodology according to claim 23 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device by operating said power converter as a boost inverter.

32. The power converter and control methodology according to claim 23 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy of said inductive load without pulse-width modulating said energization switch by controlling said energization switch depending on said energy and said voltage level of said energy device.

33. A power converter and control methodology for a switched reluctance motor having N windings, each of said windings having a first end, a second end and an energization switch, said methodology comprising the steps of:

providing a power converter having a supply bus electrically coupled to said first end of each of said N windings and a common bus electrically coupled to said second end of each of said windings, said supply bus providing phase energies to said windings according to a first set of control signals received by said energization switches for said windings, said power converter having a return bus, said return bus having a return storage device for storing energy;

monitoring operating parameters for a winding and said return bus; and

dynamically activating/deactivating said winding in response to said operating parameters of said winding and said return bus to dynamically control said energy stored in said storage device and in said winding.

34. The power converter and control methodology according to claim 33 further including the step of:

dynamically controlling said return bus in response to the operating parameters of said winding and said return bus to dynamically switch between voltage levels across said winding.

35. The power converter and control methodology according to claim 33 wherein said step of providing further includes the step of:

employing a capacitor as said storage device.

36. The power converter and control methodology according to claim 35 wherein said step of employing further includes the step of:

employing a relatively small size capacitor as said storage device.

37. The power converter and control methodology according to claim 33 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device to a voltage level higher than said supply bus.

38. The power converter and control methodology according to claim 33 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device to a voltage level lower than a predetermined value.

39. The power converter and control methodology according to claim 33 wherein said step of dynamically controlling further includes the step of:

dynamically controlling said energy stored in said storage device by operating said power converter as a boost inverter.

40. A power converter and control system for a motor having an inductive load, said system comprising:

a power converter having a supply bus electrically coupled to said inductive load, said supply bus supplying energy to said inductive load, said power converter having a return bus electrically coupled to said inductive load, said return bus electrically coupled to a storage device for storing energy; and

a controller provides control signals to said power converter, said control signals dynamically activate/deactivate said storage device and dynamically activate/deactivate said return bus.

41. A power converter and control methodology for a motor having an inductive load, said methodology comprising the steps of:

providing a power converter having a supply bus electrically coupled to a first end of said inductive load and a common bus electrically coupled to a second end of said inductive load, said supply bus supplying energy to said inductive load according to a control signal received by an energization switch, said power converter having a return bus, said return bus having a storage device for storing energy and a return bus switch which receives a second control signal; and

dynamically activating/deactivating both said inductive load and said return bus.